1. Field of the Invention
The present invention relates to seat actuators, primarily those used for vehicle seat recliners and possibly seat positioners.
2. State of the Art
As safety concerns for automobile and truck passengers increase, vehicle seats have become more complex. Linear actuators for allowing vehicle seats to move and the seat back to pivot are becoming increasingly complicated. One proposed linear actuator uses a leadscrew or threaded shaft. As it moves forward or backward axially due to the seat being reclined, a threaded gear nut or spin nut rotates about the leadscrew. The spin nut has a clutch that disengages the leadscrew when the user manually activates a recline lever. When the user releases the recline lever the clutch engages the shaft and prevents rotation of the spinning nut. That locks the leadscrew from further axial movement. Griswold, U.S. Pat. No. 5,320,413 (1994), Rees U.S. Pat. No. 4,881,775 (1989), and Periou U.S. Pat. No. 4,799,734 (1989), are examples of patents teaching this or similar types of seat actuators.
If a linear actuator is out of alignment, it can malfunction. That is, if the leadscrew is out of alignment (i.e., aligned up, down, to the side or at any angle to the gear nut), the gear nut does not spin freely around the leadscrew. Consequently, the leadscrew does not move freely backward and forward.
It has been proposed to use a gimbal mount for the entire mechanism as a way to overcome misalignment. The gimbal is expensive to manufacture and may require additional threaded fasteners that also are costly to make. Additionally, because of the added parts and the complexity of the gimbal mount, installation costs are high.